G. F. Kunz — Mineralogical Notes. 



223 



tained them from the Hawk Mica Mine, four miles east of 

 Bakersville, North Carolina. They were found at a depth of 

 380 feet, and proved to be a variety of oligoclase, remarkable 

 for its transparency. The 

 clearest piece measured '_^_. — .^ 



3x2x1 inches. In color, _ ""^T^ ^N ■* ? ^^^A 



it is a faint window-glass J^BBJ^HMPS^ 

 green, and contains a series mj ^W^W^pW^^W^W^ W "V ( 

 of cavities (see figure, natu- | %jk. &\q fy4 / /'/**& 7 



ral size), surrounded and J X ^/y^/J^wX}// / 



fringed by tufts of white f ;^MI» / 



needle-shaped microlites ; ^mmM/ '■' ii /*$ //"P'jft&fj'f J 

 these measure from 0*5 to ^K'\^-{' : ^./^ ° '* i.$n 

 l-5 mm in diameter and are T ^ ; *^ ~,sA jj^ K y/.ffl/ 

 quite round, resembling 

 those occasionally present in the Ceylonese moon-stone. 



The wonderful transparency of the oligoclase and the white 

 inclusions gives the whole mass a striking resemblance to the 

 lumps of glass, so commonly obtained from the bottom of a 

 glass pot. It was mistaken for this until the highly perfect 

 cleavage was noticed ; this is remarkable for the entire absence 

 of the striae so characteristic of the plagioclase feldspars. 



Recently some material of a slightly different character has 

 been obtained at the mine. Cleavage masses of white striated 

 oligoclase three inches long were found, containing nodules 

 about 10 to 15 mm square : these are as colorless and pellucid as 

 the finest phenacite and are entirely free from the inclusions 

 found in the greenish variety. This transparent variety like 

 the other shows no strise. 



The following analysis was very kindly furnished me by 

 Professor F. W. Clarke. It was made from the faint green 

 variety and shows it to be a typical oligoclase. The specific 

 gravity I determined to be 2 '651 : 



Si0 2 _ 62-92 



A1 2 3 25-32 



Fe. 2 3 trace 



MnO trace 



CaO 4-03 



K 2 0-96 



Na 2 6-18 



Ign _ -25 



99-66 



4. Apatite from near Yonkers, JV. Y. 



I recently received from Miss F. R. M. Plitchcock, a frag- 

 ment of an apatite crystal, which was found in the spring of 

 1887, in the tunneling at shaft 16, new Croton Aqueduct, Yon- 

 kers, Westchester County, K Y. It is 10 by 15 mm , and is 



